In order to slow the spread of HIV and improve health outcomes for persons living with HIV/AIDS (PLWHA), the Affordable Care Act greatly expands access to health care for low-income PLWHA. Further, the Office of National AIDS Policy has created a strategy to improve the current system of care by closing gaps in the HIV care continuum. The HIV care continuum outlines a series of steps in addressing infection: a) HIV testing, b) engagement in HIV care, c) participation in antiretroviral therapy (ART), and d) the ultimate target-viral suppression. Surveillance data paint a dismal picture of the continuum of care in the United States, with less than 25% of PLWHA having undetectable viral load. Given the fragmented, crisis-driven nature of the current health care system, individuals who are homeless or unstably housed may continue to receive low quality care or no care at all. The high prevalence of substance use disorders, mental illness, and other chronic illnesses among unstably housed, HIV-positive individuals increases the difficulty in engaging this group in care. The Affordable Care Act includes a number of important healthcare system restructuring provisions for chronic illness management, among which are Health Homes (HH) for Medicaid recipients. New York (NY) Department of Health (DOH) has created one of the country's earliest and most ambitious implementations of HHs. NY HH's are newly formed integrated healthcare networks of medical and behavioral health providers that contract to provide integrated care through shared care managers and common technology platforms. Additionally, NY DOH has a pilot program to provide 544 units of supportive housing (SH) for homeless PLWHA enrolled in HHs. This study will test 1) whether SH combined with HHs improves quality of care for 544 homeless PLWHA HH enrollees and 2) whether New York HH improve quality of care and costs to 8,250 Medicaid homeless PLWHA enrolled in HHs. The primary aims will be addressed in two ways. First, we will compare HIV continuum and other quality metrics and Medicaid costs between homeless PLWHA in SH and those who did not receive supportive housing using nonparametric difference-in-difference methods. Second, we will implement a longitudinal design using administrative data from 2009 through 2016 to examine changes in quality of care and Medicaid costs for homeless PLWHA in Medicaid. The project comes from an academic- public sector partnership to address high priority questions of healthcare system redesign. Data will come from surveillance data on all HIV lab tests conducted in NY, Medicaid encounters/claims, and from HHs reporting on client functioning and care manager contacts. These data will be merged to create DE identified analytical datasets by DOH. Additional qualitative research methods will be employed to elucidate the HH factors associated with outcomes. If aims are achieved, the study is likely to have a major impact on improving knowledge about evidence-based approaches to address homeless PLWHA. In addition, because the study intervention is part of ACA, the policy impact of the study findings on national healthcare may be substantial.